Shock absorber



R. C. PIERCE SHOCK ABSORBER Filed Aug. 6, 1945 velocity into the lowpressure chamber.

Patented Oct. 4, 1949 UNITED STATES PATENT OFFICE 19 Claims.

This invention relates to hydraulic shock absorber devices and moreparticularly to a novel oleo shock strut commonly utilized in theconnection between the landing gear and fuselage of an aircraft.

A general object of the invention is to provide novel means for meteringthe hydraulic fluid within the device, particularly onv the closurestroke thereof, said metering means being particularly adapted to afforda relatively large frictional area along which the fluid may flow atrelatively great velocity during metering thereof, thus increasing theamount of friction developed thereby.

A specic object of the invention is to provide a novel metering devicesuch as above described wherein a pair of plates define an intersticetherebetween communicating with ports through respective plates, theports of one plate being in communication with the high pressure chamberof the strut cylinder, and the ports of the other plate being incommunication with the low pressure chamber.

Another object of the invention is to design a` metering device such asabove described wherein the ports of respective plates are misaligned,thus preventing direct flow of hydraulic fluid through said portsbetween the high and low pressure chambers of the cylinder and directingthe uid throughthe intersticel between the plates. By means of thisarrangement the flow f of uld through the interstice increases thevelocity thereof and the heat developed by the friction of the fluidpassing through the ports is absorbed by the relatively large areas ofthe adjacent surfaces of the plates defining the interstice, whereuponthe hydraulic fiuid may iiow passively through the associated ports atrelatively low It will be understood that this passive ow preventsfoaming of the hydraulic fluid and entrapment therein of air bubbles asthe hydraulic fluid compresses the air spring disposed within the lowpressure chamber for returning the piston of the strut to its extendedposition subsequent to the closure stroke thereof.

Still another object of the invention is to design a metering devicesuch as above described, particularly adapted to accommodate by-passvalve means for opening the high and low pressure Figure 4 is a planview of the other metering plate, and Figure 5 is a sectional view takenon the line 5 5 of Figure 4.

Figure 6 is a longitudinal sectional view through a strut embodying amodication of the' invention, portions of the structure being shown inelevation.

Figure 7 is a longitudinal sectional view through a strut embodyinganother modification of the invention, portions of the structure beingshown in elevation.

Describing the invention in detail and referring first to the embodimentthereof illustrated in Figures 1-5 inclusive, the strut comprises acylinder 2 including a head 4 with a perforated bracket 6 securedthereto 'and adapted for connection to the fuselage (not shown) of anassociated aircraft. Carried by the cylinder 2 intermediate the endsthereof is a metering device or valve generally designated 8, saiddevice comprising a plate or bulkhead I0 secured in any convenientmanner to the cylinder 2, as by welding. The plate I0 divides thecylinder into a high pressurechamber I2 and a low pressure chamber I4,the latter con'- taining at its upper extremity an air spring comprisinga body of compressed air introduced into the cylinder through Aaconventional fitting or valve I6. A piston I8 is slidably fitted withinthe cylinder 2 in the high pressure chamber I2 thereof "forreciprocation therewithin.

A plate 20 is secured by a bolt and nut assembly 22 to the plate I0,said plate 20 comprising an annular ange 24 on the lower surface thereofdening an annular recess 26 aording an interstice between the plates I0and 20. This interstice is exaggerated in the drawings and is preferablyof the order of six to twelve-thousandths of an inch in depth so as toaccommodate a relatively chambers to direct communication on theextension stroke of the strut to insure rapid release or extensionthereof.

In the drawings, Figure 1 is a longitudinal sectional view through astrut embodying the inven-l tion, portions of the structure being shownin elevation.

Figure 2 is a plan view of one of the metering plates, and Figure 3 is asectional view takenon the line 3-3 of Figure 2.

thin layer of hydraulic fluid owing therethrough, thereby enablingrelatively eiiicient heat transfer between the iiuid flowing through theinterstice and the. plates I0 and 20. A plurality of annular grooves 28,28 are formed in the lower surface of the plate y2t communicating withports or flow passages 30, 30 therethrough, said passages communicatingwith the low pressure chamber I4.

It may be noted that the passages 34, 34 are preferably approximatelyequidistantly spacedbetween the radially inner passages 30 and the'radially outer passages 30, whereby on the compression or meteringstroke of the strut, the hydraulic fluid mayl flow therethrough underapproximately equal resistance into all of the passages 30.

The plate I0 is formed on its upper surface with an .annular groove 32disposed between the grooves 28, 28 and communicating with a pluralityof ports or iiow passages 34, 34 connected to the high pressure chamberI2;

By-pass valve means, generally designated 36,

is provided for by-passing the metering device on-the extension strokeof the strut, said valve means 36 comprising an annular flapper plate 30mounted on a plurality of pins or stud bolts 40, 40, each of whichcarries a relatively weak spring 42 adapted to urge the plate intoengagement with the lower ends of ports or flow passages 44, 44extending through the plate l0 around the plate 20. The :dapper plate 38comprises a central opening 46 through which the hydraulic medium withinthe cylinder 2 may be urged on the closure stroke of the piston I8.

Thus as the piston |8 is urged'upwardly on its -closure stroke withinthe high pressure chamber l2, the hydraulic fluid within the cylinder isurged from the high pressure chamber |2 through the opening 46 andthefports 34, 34. As the hydraulic fluid passes through the intersticeaorded by the recess 26. the velocity of the iluid is increased, andheat is absorbed along the relatively large areas aiorded by theadiacent surfaces of the plates I0 and l20. The fluid passes into thelow pressure chamber |4 through the ports 30, 30 at relatively lowvelocity, thereby avoiding foaming of the hydraulic fluid within thechamber |4. It may be noted that the ports 30, 30 are angularly relatedto the longitudinal axis of ,the cylinder 2, whereby hydraulic uidpassing from these ports into the chamber |4 is directed against theadjacent cylinder surface to further decrease the velocity of said iiuidand prevent foaming thereof.

On the extension stroke of the piston i8, as it moves downwardly withinthe chamber |2, the air spring forces the hydraulic fluid through theports 44, 44, moving the apper plate 38 to its open position against theresistance of the relatively weak springs 42, 42, as shown in Figure 1,thereby facilitating rapid release or extension of Athe strut.

Figure 6 illustrates a modication of the invention wherein partscorresponding to those shown in Figure 1 are identified by the samenumerals. In this embodiment of the invention, the plate 20 is urgedinto engagement with the bulkhead or plate I0 by means of a spring 48adiustably compressed against plate 20. The spring is oompressed by apin the head 4 of the cylinder 2, said pin having a cylindrical nose 52slidably tted within a hollow boss 54 of a spring cap 56 bearing,against the top of the spring 48. By means of this arrangement, theplate 20 is reslliently urged under adjustable pressure against theplate I0, thus accommodating movement of the plate 20 away from theplate l0 tov enlarge the interstice between the plates. It will beunderstood that by adjusting the pressure of the spring 48. anadjustable metering eect may be obtained and, if desired, the recess 26in the bottom of the plate 20 may be eliminated inasmuch as theinterstice between the plates may be created by the above-mentionedmovement of the plate 20 away from the plate |0. Figure 7 illustratesanother modification of the inventionwherein the cylinder |02 is dividedby a bulkhead wall or plate |04 into high and low chambers |06 and |08respectively, a piston ||0 being reclprocated within the high pressurechamber. A bolt or pin ||2 is secured to the plate |04 as by threadedengagement therewith, the lower end of the pin ||2 being D10vided with anut ||4 adapted to compress a relatively weak spring ||6 against a plateM8 which is thereby urged against the before-mentioned plate |04. Theplate |04 is provided with a plurality of ports |20 communicating withan annular groove |22,

and the plate ||8 is provided with a plurality of radially inner ports|24 communicating with an annular groove |26. and a plurality ofradially outer ports |28 communicating with an annular groove |30. Theupper surface of the plate ||8 is recessed as at |32 to provide aninterstice between the plates |04 and H6.

In this embodiment of the invention, on the closure stroke of the strut,theV hydraulic fluid within the high pressure chamber |06 ls forcedthrough the ports |24 and |28 into the interstice at |32 and upwardlytherefrom through the ports into the low pressure chamber |08 therebyeffecting a metering of the hydraulic fluid within the cylinder |02. 0nthe expansion or release stroke of the device, the pressure within theinterstice |32 is greater than that within the chamber |06, thus forcingthe plate |24 downwardly against the resistance of spring ||6 to permita great amount of the hydraulic fluid to ow from the ports |20 aroundthe plate ||8 and into the high pressure chamber |06 without passingthrough the ports |24 and |28, so that the metering action, if any, isnegligible on the release stroke of the device.

It is to be understood that I do not wish to be limited by the exactembodiments of the device shown which are merely by way of illustrationand not limitation as various and other forms of the device will, ofcourse, be apparent to those skilled in the art without departing fromthe spirit of the invention or the scope of the claims.

I claim:

l. In a shock strut, a cylinder containing hydraulicuid, valve meanscarried by said cylinder internally thereof for metering said uid, saidvalve means comprising a wall within said cylinder dividing the sameinto axially spaced chambers, a valve plate, ports through said platecomin threaded engagement with v municating with an interstice betweensaid plate and said wall and communicating with one of said chambers,ports through said wall communieating with the other chamber and withsaid interstice, the ports throughv said wall being misalignedwithrespect` to the ports through said plate, a piston slidably itted withinone of said chambers for reciprocation therewithin, ports through saidwall around the margins of said plate and communicating with saidchambers, and valve means for-accommodating direct communication betweensaid chambers through said-lastmentioned ports independently of saidiirst and second-mentioned ports on the extension stroke of the strut.

2. In a shock strut, a cylinder containing hydraulic fluid, valve meanscarried by said cylinder internally thereof for metering said uid, saidvalve means comprising a wall member withinsaid cylinder dividing thesame into axially spaced chambers, a valve plate member, ports throughsaid plate member communicating with anintersticebetweensaid members andcommunicating with one of said chambers, ports through said wall membercommunicating with the other chamber and with said interstice, the portsthrough said wall member being msaligned with respect to the portsthrough said plate member, and a piston slidablytted within one -oi saidchambers for reciprocation therewthin, the ports tioned ports on theextension stroke of the strut,

and a piston slidably tted within said cylinder for reciprocationtherewithin.

' and a plurality of ports through each plate mis- 4. In a shock strut,a cylinder containing hydraulic uid, valve means carried by saidcylinder internally thereof for metering said uid, said valve meanscomprising a wall vwithin said cylinder-dividing the same into axiallyspaced chambers, one of said chambers being a low pressure chamber andthe other of said chambers being a high pressure chamber, a valve plate,ports through said plate communicating with an interstice between saidplate and said wall and communicating with said one chamber, portsthrough said wall communicating with the other chamber and with saidinterstice, the ports through said wall being misaligned with respect tothe ports through said plate, and a piston slidably fitted within saidother chamber for reciprocation therewithin, the ports in said platediverging with respect to the longitudinal axis of said strut fordirecting iiuid against the sides of said cylinder on the closure strokeof said strut to prevent foaming of said fluid.

5. In a hydraulic shock strut, a cylinder, a bulkhead fixed thereindividing said cylinder into high and low pressure chambers, a plate inthe low pressure chamber dening an interstice with said bulkhead, portsthrough said plate communicating with said interstice and with said lowpressure chamber, ports through said bulkhead communieating with saidinterstice and with said high pressure chamber, and a piston slidably`iitted within said high pressure chamber for reciprocation therewithin,the ports through said bulkhead being misaligned with respect to theports through said plate, the ports in said plate being disposed at anacute angle with respect to the wall of said cylinder for directingiiuidthereagainst on the closure stroke of said strut to prevent foamingofsaid uid.

6. In a hydraulic shock strut, a cylinder, a bulkhead iixed thereindividing said cylinder into high and low pressure chambers, a plate inthe low pressure chamber defining an interstice with said bulkhead, aplurality of concentric annular grooves in the adjacent sides of saidbulkhead and plate and communicating with said interstice,

ports through said plate communicating with the grooves therein and withsaid low pressure chamber, ports through said bulkhead communicatingwith the grooves therein and with said high pressure chamber, a pistonslidably tted within said high pressure chamber for reciprocationtherewithin, and by-pass valve means for accommodate ing ow of iiuidbetween said chambers on the extension stroke only of the strut.

7. In avhydraulic shock absorber device, a cylinder containing an airspring at its upper end and a body of hydraulic iiuid adapted tocompress said spring, means mounted in said cylinder for metering saidiiuid, said means comprising a pair of abutting plates, an intersticetherebetween,

. said cylinder, a.

I bulkhead sides of said plates concentrically arrangedwith respect toeach other and communicating with said interstice, and a plurality ofports through each plate misaligned with respect to the ports of ,theother plate and communicating with the channels in their respectiveplates, a piston reciprocal within said cylinder, and valve means forby-passing said ports on the extension stroke only of the device tofacilitate rapid extension thereof.

9. In a shock strut, a cylinder containing hydraulic iiuid, a bulkheadmember iixed within said cylinder dividing the same into axially spacedchambers, a valve plate member mounted within said cylinder and deiiningan interstice with said bulkhead member, a plurality of alternatelyarranged annular grooves in the adjacent surfaces of respective memberscommunicating with said interstice, ports through respective membersconnected to the grooves therein, spring-seating means within saidcylinder, spring means seated against said plate and said last-mentionedmeans and reacting therebetween for against said bulkhead member, and apiston slidably iitted within said cylinder for reciprocationtherewithin, said plate member at its marginal edges being spaced fromsaid cylinder and being movable away from said bulkhead member againstthe resistance of said spring means to enlarge the interstice betweensaid members under certain closure conditions of said strut whereby saidfluid is permitted escape between said members and between the marginaledges of said plate member and said cylinder and into the adjacent ofsaid chambers.

10. In a shock strut, a cylinder containing hydraulic fluid, abulkheadmember fixed within said cylinder, a', valve plate member mounted on themember and deiining an interstice with said bulkhead member and spacedat its edges from said cylinder, a plurality of alternately arrangedannular grooves in the adjacent surfaces of said members communicatingwith said interstice, ports through respective members communicatingwith the grooves therein, spring means within said cylinder urging saidplate member against said bulkhead member, said plate member on theextension stroke of said strut being movable away from said bulkheadmember for thus aifording a passage for said fluid between said membersand thence around the edges of said plate member and the adjacent sideof said cylinder independently of the ports in said plate member,whereby rapid extension of said strut is facilitated, and a pistonslidably fitted within said cylinder for reciprocation therewithin.

11. In a shock strut, a cylinder containing hydraulic fluid, a bulkheadmember iixed within valve plate member mounted within said cylinder anddefining an interstice with' said bulkhead member, spring-seating meanswithin said cylinder, spring means compressed by and between said valveplate and said urging said plate,

